Abstract:

An indoor unit includes an indoor side transmitting and receiving section,
a relay which is put in a closed state in a standby state, and an indoor
control section which controls the relay on the basis of an output of the
indoor side transmitting and receiving section. An outdoor unit includes
an outdoor side transmitting and receiving section, and a power circuit.
Then, the indoor control section of the indoor unit does not bring the
relay into the closed state upon determining that the connection wiring
lines which connect the indoor unit with the outdoor unit are miswired on
the basis of a reception output of the indoor side transmitting and
receiving section when operation starts from a standby state in which the
supply of power of the outdoor unit is stopped.

Claims:

1. An air conditioner comprising:an indoor unit and an outdoor unit which
are connected via connection wiring;the connection wiring comprising two
power lines for supplying a power from an external power source via one
of the indoor unit and the outdoor unit to the other of the indoor unit
and the outdoor unit, and one signal line for carrying out communication
between the indoor unit and the outdoor unit;the indoor unit comprising
an indoor side switch device which is connected between one of the power
lines and the signal line and brought into a closed state at a startup
time when operation starts from a standby state in which the supply of
power of the outdoor unit is stopped, andthe outdoor unit comprising a
startup power supply switch device which is brought into a closed state
so that a power for startup is supplied from the indoor unit side via the
signal line when the indoor side switch device of the indoor unit is
brought into the closed state, an operating power supply switch device
which is brought into a closed state so that the power for operation is
supplied to a load via the power line in operation while is brought into
an open state in the standby state, and an outdoor control device which
controls the operating power supply switch device and the startup power
supply switch device, whereinthe outdoor control device of the outdoor
unit brings the startup power supply switch device into the closed state
when the operation starts from the standby state by supplying a power for
startup from the indoor unit side via the signal line and the startup
power supply switch device as a consequence that the indoor side switch
device of the indoor unit is brought into the closed state and thereafter
brings the operating power supply switch device into the closed state
after a lapse of a prescribed time.

2. The air conditioner as claimed in claim 1, whereinthe indoor unit
comprises an indoor side transmitting and receiving device connected to
the signal line; an indoor control device which controls the indoor side
switch device and the indoor side transmitting and receiving device, and
an informing device for informing a user of miswiring,the outdoor unit
comprises an outdoor side transmitting and receiving device which is
connected to the signal line and carries out communication with the
indoor side transmitting and receiving device, andthe indoor control
device determines that the connection wiring lines which connect the
indoor unit with the outdoor unit are miswired when no communication with
the outdoor side transmitting and receiving device can be achieved by the
indoor side transmitting and receiving device after bringing the indoor
side switch device into the closed state to start operation from the
standby state and informs the user of miswiring by the informing device.

Description:

[0001]This application is a Divisional of co-pending application Ser. No.
11/791,698, filed on May 25, 2007, the entire contents of which are
hereby incorporated by reference and for which priority is claimed under
35 U.S.C. §120.

TECHNICAL FIELD

[0002]The present invention relates to an air conditioner having an indoor
unit and an outdoor unit connected via connection wiring.

BACKGROUND ART

[0003]Conventionally, there has been proposed an air conditioner, which is
externally supplied with a power by an outdoor unit and able to reduce
the power consumption in a standby state of an indoor unit and the
outdoor unit by limiting the supply of a main power to each part via a
power line in the standby state (refer to, for example, JP 2000-111123
A). The air conditioner includes the indoor unit, the outdoor unit and a
signal line for transmitting and receiving a transmission signal between
the indoor unit and the outdoor unit.

[0004]Since the transmission of the transmission signal via the signal
line has been performed by an AC power in the conventional air
conditioner, its transmission speed depends on the frequency and tends to
have difficulties in being increased in speed. On the other hand, it has
been concerned that, when a power supply is newly provided to increase
the speed of the transmission of the transmission signal via the signal
line, the power consumptions in the standby state of the indoor unit and
the outdoor unit be increased due to the provision of the power supply.

[0005]Accordingly, in order to solve such a problem, the present applicant
has proposed an air conditioner and a control method capable of
transmitting the transmission signal at high speed and reducing the power
consumption in the standby state of the indoor unit and the outdoor unit.
It is noted that the air conditioner and the control method are intended
for easy understanding of the present invention and neither a known art
nor a prior art.

[0006]In the air conditioner, a relay is provided between one of power
lines that connect the indoor unit with the outdoor unit and the signal
line, and an operating power supply relay of the outdoor unit is turned
on by transmitting a power for startup to the outdoor unit using the
signal line by turning on the relay for a prescribed time when the
operation starts from the standby state in which the power of the outdoor
unit is cut off.

[0007]However, it is sometimes the case where, when the connection wires
are miswired by mistake in connecting the indoor unit with the outdoor
unit by connection wiring lines in the air conditioner, a closed circuit
including a power source is formed between a part on the indoor unit side
and a part on the outdoor unit side, and this disadvantageously leads to
the damage of components.

DISCLOSURE OF THE INVENTION

[0008]Accordingly, it is an object of the present invention to provide an
air conditioner capable of preventing the damage of components with a
simple construction even when the operation starts in a state in which
the connection wiring lines that connect the indoor unit with the outdoor
unit are miswired.

[0009]In order to achieve the above object, an air conditioner according
to the first inventive aspect comprises:

[0010]an indoor unit and an outdoor unit which are connected via
connection wiring;

[0011]the connection wiring comprising two power lines for supplying a
power from an external power source to the indoor unit via the outdoor
unit, and one signal line for c arrying out communication between the
indoor unit and the outdoor unit;

[0012]the indoor unit comprising an indoor side transmitting and receiving
means which is connected to the signal line and employs a photocoupler,
an indoor side switch means which is connected between one of the power
lines and the signal line and brought into a closed state at a startup
time when operation starts from a standby state in which the supply of
power of the outdoor unit is stopped, and an indoor control means which
controls the indoor side switch means; and

[0013]the outdoor unit comprising an outdoor side transmitting and
receiving means which is connected to the signal line and employs a
photocoupler, and a load which is supplied with a power from the two
power lines of the connection wiring, wherein

[0014]the indoor control means of the indoor unit does not bring the
indoor side switch means into the closed state upon determining that the
connection wiring lines which connect the indoor unit with the outdoor
unit are miswired on the basis of a reception output of the indoor side
transmitting and receiving means when the operation starts from the
standby state.

[0015]For example, in a case where the connection wiring lines are
connected partially exchanged by connecting the terminal to which the
signal line of the indoor unit should be connected with the terminal to
which the other of the power lines of the outdoor unit should be
connected and connecting the terminal to which the signal line of the
outdoor unit should be connected with the terminal to which the other of
the power lines of the indoor unit should be connected, a closed circuit
is formed of part of the indoor unit, part of the outdoor unit and the
power source via the indoor side switch means when the indoor side switch
means is directly brought into the closed state at the startup time when
the operation starts from the standby state in which the power supply of
the outdoor unit is stopped, and an overcurrent flows through the
circuit, disadvantageously damaging the components. In contrast to this,
according to the air conditioner of the above construction, the indoor
control means of the indoor unit determines that the connection wiring
lines which connect the indoor unit with the outdoor unit are miswired on
the basis of the reception output of the indoor side transmitting and
receiving means when the operation starts from the standby state in the
miswired state as described above. That is, in the case of the miswiring
as described above, it becomes possible to determine that the connection
wiring lines are miswired before the indoor side switch means is brought
into the closed state by applying the power voltage to the signal line to
turn on the reception output of the indoor side transmitting and
receiving means. Therefore, even if the operation starts in the state in
which the connection wiring lines that connect the indoor unit with the
outdoor unit are miswired, the damage of components can be prevented with
a simple construction employing the indoor side transmitting and
receiving means.

[0016]In the air conditioner of one embodiment, the indoor control means
of the indoor unit determines that the connection wiring lines which
connect the indoor unit with the outdoor unit are miswired when the
reception output of the indoor side transmitting and receiving means is
turned on at the time of starting the operation from the standby state in
which the supply of power of the outdoor unit is stopped.

[0017]According to the air conditioner of the above embodiment, it becomes
possible to easily determine that the connection wiring lines are
miswired before the indoor side switch means is brought into the closed
state by applying the power voltage to the signal line to turn on the
reception output of the indoor side transmitting and receiving means in
the miswired state as described above.

[0018]In the air conditioner of one embodiment,

[0019]the indoor unit comprises an informing means for informing a user of
miswiring, and

[0020]the indoor control means informs the user of miswiring by the
informing means upon determining that the connection wiring lines which
connect the indoor unit with the outdoor unit are miswired.

[0021]According to the air conditioner of the above embodiment, the
informing means informs the user of the miswiring upon determining that
the connection wiring lines are miswired. Therefore, the operator is able
to perceive the cause of the trouble at the time of installation and to
swiftly cope with the trouble.

[0022]In order to achieve the above object, an air conditioner according
to the second inventive aspect comprises:

[0023]an indoor unit and an outdoor unit which are connected via
connection wiring;

[0024]the connection wiring comprising two power lines for supplying a
power from an external power source via one of the indoor unit and the
outdoor unit to the other of the indoor unit and the outdoor unit, and
one signal line for carrying out communication between the indoor unit
and the outdoor unit;

[0025]the indoor unit comprising an indoor side switch means which is
connected between one of the power lines and the signal line and brought
into a closed state at a startup time when operation starts from a
standby state in which the supply of power of the outdoor unit is
stopped, and

[0026]the outdoor unit comprising a startup power supply switch means
which is brought into a closed state so that a power for startup is
supplied from the indoor unit side via the signal line when the indoor
side switch means of the indoor unit is brought into the closed state, an
operating power supply switch means which is brought into a closed state
so that the power for operation is supplied to a load via the power line
in operation while is brought into an open state in the standby state,
and an outdoor control means which controls the operating power supply
switch means (MRM10) and the startup power supply switch means, wherein

[0027]the outdoor control means of the outdoor unit brings the startup
power supply switch means into the closed state when the operation starts
from the standby state by supplying a power for startup from the indoor
unit side via the signal line and the startup power supply switch means
as a consequence that the indoor side switch means of the indoor unit is
brought into the closed state and thereafter brings the operating power
supply switch means into the closed state after a lapse of a prescribed
time.

[0028]For example, in a case where the connection wiring lines are
connected partially exchanged by connecting the terminal to which the
signal line of the indoor unit should be connected with the terminal to
which the other of the power lines of the outdoor unit should be
connected and connecting the terminal to which the signal line of the
outdoor unit should be connected with the terminal to which the other of
the power lines of the indoor unit should be connected, a closed circuit
is formed of part of the indoor unit, part of the outdoor unit (including
the operating power supply switch means and the startup power supply
switch means) and the power source via the indoor side switch means when
the indoor side switch means is directly brought into the closed state at
the startup time when the operation starts from the standby state in
which the power supply of the outdoor unit is stopped, and an overcurrent
flows through the circuit, disadvantageously damaging the components. In
contrast to this, according to the air conditioner of the above
construction, the operating power supply switch means is brought into the
closed state after a lapse of the prescribed time after the startup power
supply switch means is brought into the open state by the outdoor control
means of the outdoor unit when the operation starts from the standby
state by supplying the power for the startup from the indoor unit side to
the outdoor unit side via the indoor side switch means and the signal
line as a consequence that the indoor side switch means of the indoor
unit is brought into the closed state. That is, by bringing the startup
power supply switch means into the open state before the operating power
supply switch means is brought into the closed state, no closed circuit
is formed of part of the indoor unit and part of the outdoor unit via the
indoor side switch means. Therefore, even when the operation starts in
the state in which the connection wiring lines that connect the indoor
unit with the outdoor unit are miswired, damage of the components can be
prevented with a simple construction.

[0029]In the air conditioner of one embodiment,

[0030]the indoor unit comprises an indoor side transmitting and receiving
means connected to the signal line; an indoor control means which
controls the indoor side switch means and the indoor side transmitting
and receiving means, and an informing means for informing a user of
miswiring,

[0031]the outdoor unit comprises an outdoor side transmitting and
receiving means which is connected to the signal line and carries out
communication with the indoor side transmitting and receiving means, and

[0032]the indoor control means determines that the connection wiring lines
which connect the indoor unit with the outdoor unit are miswired when no
communication with the outdoor side transmitting and receiving means can
be achieved by the indoor side transmitting and receiving means after
bringing the indoor side switch means (MR10) into the closed state to
start operation from the standby state and informs the user of miswiring
by the informing means.

[0033]According to the air conditioner of the above embodiment, when no
communication with the outdoor side transmitting and receiving means can
be achieved by the indoor side transmitting and receiving means after the
indoor side switch means is brought into the closed state, the indoor
control means determines that the connection wiring lines are miswired
and informs the user of the miswiring by the informing means. Therefore,
the operator is able to perceive the cause of the trouble at the time of
installation and to swiftly cope with the trouble.

[0034]As is apparent from the above, according to the air conditioner of
the first inventive aspect, the indoor control means of the indoor unit
determines that the connection wiring lines which connect the indoor unit
with the outdoor unit are miswired on the basis of the reception output
of the indoor side transmitting and receiving means when the operation
starts from the standby state in the miswired state and does not bring
the indoor side switch means into the closed state. With this
arrangement, damage of the components can be prevented with a simple
construction even when the operation starts in the miswiring state in
which the connection wiring lines which connect the indoor unit with the
outdoor unit are miswired.

[0035]Moreover, according to the air conditioner of the above embodiment,
it becomes possible to easily determine that the connection wiring lines
are miswired before the indoor side switch means is brought into the
closed state by applying the power voltage to the signal line to turn on
the reception output of the indoor side transmitting and receiving means
in the miswired state as described above.

[0036]Moreover, according to the air conditioner of one embodiment, by
informing the user of the miswiring by the informing means when the
indoor control means determines that the connection wiring lines are
miswired, the operator is able to perceive the cause of the trouble at
the time of installation and to swiftly cope with the trouble.

[0037]Moreover, according to the air conditioner of the second inventive
aspect, the operating power supply switch means is brought into the
closed state after a lapse of the prescribed time after the startup power
supply switch means is brought into the open state by the outdoor control
means of the outdoor unit when the operation starts from the standby
state by supplying the power for the startup from the indoor unit side to
the outdoor unit side via the indoor side switch means and the signal
line as a consequence that the indoor side switch means of the indoor
unit is brought into the closed state. Therefore, even when the operation
starts in the state in which the connection wiring lines that connect the
indoor unit with the outdoor unit are miswired, damage of the components
can be prevented with a simple construction.

[0038]Moreover, according to the air conditioner of one embodiment, when
no communication with the outdoor side transmitting and receiving means
can be achieved by the indoor side transmitting and receiving means after
the indoor side switch means is brought into the closed state, the indoor
control means determines that the connection wiring lines are miswired
and informs the user of the miswiring by the informing means. With this
arrangement, the operator is able to perceive the cause of the trouble at
the time of installation and to swiftly cope with the trouble.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039]The present invention will become more fully understood from the
detailed description given hereinbelow and the accompanying drawings
which are given by way of illustration only, and thus are not limitative
of the present invention, and wherein:

[0040]FIG. 1 is a block diagram of an air conditioner according to a first
embodiment of the present invention;

[0041]FIG. 2 is a circuit diagram of an indoor side transmitting and
receiving section of the air conditioner;

[0042]FIG. 3 is a circuit diagram of an outdoor side transmitting and
receiving section of the air conditioner;

[0043]FIG. 4 is a circuit diagram of an EMI filter of an outdoor unit of
the air conditioner;

[0044]FIG. 5A is a connection diagram in a case of miswiring of the air
conditioner;

[0045]FIG. 5B is a diagram showing a state when a MR10 is turned on in the
case of miswiring of the air conditioner;

[0046]FIG. 6 is a timing chart showing processing when the air conditioner
starts operating from a standby state;

[0047]FIG. 7 is a block diagram of an air conditioner according to a
second embodiment of the present invention;

[0048]FIG. 8 is a connection diagram in a case of miswiring of the air
conditioner;

[0049]FIG. 9A is a connection diagram for explaining correct wiring of the
air conditioner;

[0050]FIG. 9B is a connection diagram for explaining miswiring of the air
conditioner;

[0051]FIG. 9C is a connection diagram for explaining miswiring of the air
conditioner;

[0052]FIG. 9D is a connection diagram for explaining miswiring of the air
conditioner;

[0053]FIG. 9E is a connection diagram for explaining miswiring of the air
conditioner;

[0054]FIG. 9F is a connection diagram for explaining miswiring of the air
conditioner;

DETAILED DESCRIPTION OF THE INVENTION

[0055]The air conditioner of the present invention will now be described
in detail below by the embodiments shown in the drawings.

FIRST EMBODIMENT

[0056]FIG. 1 is a block diagram of the air conditioner of the first
embodiment of the present invention, showing an indoor unit 10, an
outdoor unit 20 connected to the indoor unit 10 via connection wiring
lines (L1 through L3), and an external power source 30 connected to the
outdoor unit 20.

[0057]The indoor unit 10 includes a power circuit 11 that has one terminal
connected to the power line L1 and has the other terminal connected to
the power line L2, an indoor side transmitting and receiving section 15
as one example of the indoor side transmitting and receiving means that
has one terminal connected to one terminal of the signal line L3 and has
the other terminal connected to the power line L2, and a relay MR10 as
one example of the indoor side switch means connected between the power
line L1 and the signal line L3, the relay MR10 being normally in an open
state. The indoor unit 10 also includes an indoor control section 12 as
one example of the indoor control means that is supplied with a power
from the power circuit 11 and controls the relay MR10 and so on, and a
display section 13 as one example of the informing means controlled by
the indoor control section 12. A power voltage supplied from the external
power source 30 is applied across both terminals of the power circuit 11
via the power lines L1 and L2.

[0058]On the other hand, the outdoor unit 20 includes an EMI filter LC1
that have input terminals (T1 and T2 shown in FIG. 4) connected to the
power lines L1 and L2, an outdoor side transmitting and receiving section
25 as one example of the outdoor side transmitting and receiving means
connected to the other terminal of the signal line L3, a transmission
power circuit 24 that has one terminal connected to the signal line L3
via a switchover relay MR30 and supplies a power to the outdoor side
transmitting and receiving section 25, a switching power circuit 22 that
has one terminal connected to the signal line L3 via the switchover relay
MR30, and a power circuit 23 as one example of the load that has one
terminal connected via a relay MRM10 to one terminal (T3 shown in FIG. 4)
of the output terminals of the EMI filter LC1. The other terminal of the
switching power circuit 22 is connected to the other terminal (T4 shown
in FIG. 4) of the output terminals of the EMI filter LC1, and the other
terminal of the power circuit 23 is connected to the other terminal of
the output terminals of the EMI filter LC1 via a relay MRM11. Moreover, a
relay MRM20 and a resistor R11 are connected to both terminals of the
relay MRM10 serially in order from the EMI filter LC1 side. The outdoor
unit 20 also includes an outdoor control section 21 as one example of the
outdoor control means that is supplied with a power from the switching
power circuit 22 and controls the relays MRM10, MRM20, MRM11, MR30 and so
on. The resistor R11 prevents an overcurrent from flowing through the
relay MRM11 and the relay MRM20 when power supply starts from the standby
state.

[0059]The switchover relay MR30 has input terminals 1 and 2 and an output
terminal 3. The input terminal 1 is connected to the signal line L3, the
input terminal 2 is connected to one terminal (T3 shown in FIG. 4) of the
output terminals of the EMI filter LC1, and the output terminal 3 is
connected to one terminal of the switching power circuit 22. The
switchover relay MR30, which connects the signal line L3 with the
transmission power circuit 24 in the OFF state, releases the connection
between the signal line L3 and the transmission power circuit 24 in the
ON state and connects one (T3 shown in FIG. 4) of the output terminals of
the EMI filter LC1 with the transmission power circuit 24.

[0060]The transmission power circuit 24 has a resistor R1 that has one
terminal connected to the signal line L3 via a switchover relay MRM30, a
diode D1 of which the anode is connected to the other terminal of the
resistor R1, a zener diode ZD1 of which the cathode is connected to the
cathode of diode D1 and the anode is connected to the power line L2, a
smoothing capacitor C1 connected in parallel with the zener diode ZD1,
and a resistor R2 connected in parallel with the zener diode ZD1. The
resistor R2 prevents an overvoltage from being applied across both
terminals of the zener diode ZD1 and the smoothing capacitor C1.

[0061]An AC voltage supplied from the power lines L1 and L2 shown in FIG.
1 is half-wave rectified by the diode D1 and smoothed by a smoothing
capacitor C1. The smoothed DC voltage is regulated to a constant voltage
by the zener diode ZD1 and supplied to the outdoor side transmitting and
receiving section 25.

[0062]FIG. 2 shows a circuit diagram of the indoor side transmitting and
receiving section 15. As shown in FIG. 2, the indoor side transmitting
and receiving section 15 includes a diode D151 of which the anode is
connected to a terminal 151, a resistor R151 that has one terminal
connected to the cathode of the diode D151, a phototransistor Q151 of
which the collector is connected to the other terminal of the resistor
R151, a light-emitting diode D152 of which the anode is connected to the
emitter of the phototransistor Q151 and the cathode is connected to a
terminal 152, a zener diode ZD151 of which the cathode is connected to
the collector of the phototransistor Q151 and the anode is connected to
the emitter of the phototransistor, and a resistor R152 connected in
parallel with both terminals of the light-emitting diode D152. Moreover,
in the indoor side transmitting and receiving section 15, a photocoupler
is constructed of a pair of the phototransistor Q151 and a light-emitting
diode (not shown), and a photocoupler is constructed of a pair of the
light-emitting diode D152 and a phototransistor (not shown), enabling
two-way communications. The terminal 151 of the indoor side transmitting
and receiving section 15 is connected to the communication line L3, and
the terminal 152 is connected to the power line L2.

[0063]The resistor R151 limits the current that flows through the
phototransistor Q151 and the light-emitting diode D152, and the diode
D151 prevents the current from flowing backward. The zener diode ZD151
prevents an overvoltage from being applied across both terminals of the
phototransistor Q151, and the resistor R152 prevents an overvoltage from
being applied across both terminals of the light-emitting diode D152.

[0064]FIG. 3 shows a circuit diagram of the outdoor side transmitting and
receiving section 25. As shown in FIG. 3, the outdoor side transmitting
and receiving section 25 includes a diode D251 of which the cathode is
connected to a terminal 251, a resistor R251 that has one terminal
connected to the anode of the diode D251, a light-emitting diode D252 of
which the cathode is connected to the other terminal of the resistor
R251, a resistor R252 connected in parallel with both terminals of the
light-emitting diode D252, a phototransistor Q251 of which the emitter is
connected to the anode of the light-emitting diode D252 and the collector
is connected to a terminal 252, a resistor R253 connected between the
collector and the emitter of the phototransistor Q251, a zener diode
ZD251 of which the anode is connected to the collector of the
phototransistor Q251, and a zener diode ZD252 of which the anode is
connected to the cathode of the zener diode ZD251 and the cathode is
connected to the emitter of the phototransistor Q251. Moreover, in the
indoor side transmitting and receiving section 15, a photocoupler is
constructed of a pair of the phototransistor Q251 and a light-emitting
diode (not shown), and a photocoupler is constructed of a pair of the
light-emitting diode D252 and a phototransistor (not shown), enabling
two-way communications. The terminal 251 of the outdoor side transmitting
and receiving section 25 is connected to the communication line L3, and
the terminal 252 is connected to the transmission power circuit 24.

[0065]The diode D251 prevents the current from flowing backward, and the
resistor R251 limits the current that flows through the phototransistor
Q251 and the light-emitting diode D252. The resistor R252 prevents an
overvoltage from being applied across both terminals of the
light-emitting diode D252, and the resistor R253 prevents an overcurrent
from flowing through the phototransistor Q251.

[0066]FIG. 4 shows a circuit diagram of the EMI filter LC1 of the outdoor
unit of the air conditioner. As shown in FIG. 4, the EMI filter LC1 has a
coil L11 that has one terminal connected to a terminal T1, a coil L12
that has one terminal connected to a terminal T2 and forms a mutual
inductance with the coil L11, a coil L13 that has one terminal connected
to the other terminal of the coil L11 and has the other terminal
connected to a terminal T3, a coil L14 that has one terminal connected to
the other terminal of the coil L12 and has the other terminal connected
to a terminal T4, a capacitor C12 that has one terminal connected to the
other terminal of the coil L13 and has the other terminal grounded, a
capacitor C13 that has one terminal connected to the other terminal the
coil L14 and has the other terminal connected to the other terminal of
the capacitor C12, and a capacitor C11 connected between the terminal T3
and the terminal T4.

[0067]The terminal T1 of the EMI filter LC1 is connected to the power line
L1 (shown in FIG. 1), and the terminal T2 is connected to the power line
L2 (shown in FIG. 1). The terminal T3 is connected to the relays MRM10
and MRM20 (shown in FIG. 1), and the terminal T4 is connected to the
switching power circuit 22 and MRM11 (shown in FIG. 1).

[0068]In the EMI filter LC1, a first noise generated in the power circuit
23 (shown in FIG. 1) is inputted to the terminal T3 via the power line L1
(shown in FIG. 1) and inputted to the terminal T4 via the power line L2
(shown in FIG. 1). The first noise has mainly a low-frequency normal-mode
noise and a high-frequency common-mode noise. The low-frequency
normal-mode noise has its frequency components of not lower than the
cutoff frequency removed by the operation of a low-pass filter
constructed of the capacitor C11, the coil L13 and the coil L14. On the
other hand, the high-frequency common-mode noise has its frequency
components of not lower than the cutoff frequency removed by the
operation of a low-pass filter constructed of the capacitor C12, the
capacitor C13, the coil L11 and the coil L12.

[0069]As shown in FIG. 1, with regard to the relay MR10 of the indoor unit
10, the relay MR10 is closed by an indoor microcomputer 12 when the
operation is switched over from the standby state to the operating state,
so that the main power is supplied from the power line L1 to the signal
line L3. That is, a rise in the voltage of the signal line L3 serves as a
signal of switchover from the standby state to the operating state.

[0070]In the air conditioner of the above construction, it is correct to
connect the wiring lines L1 through L3 at the time of installation in a
manner that the terminals AC, terminals S and terminals COM of the indoor
unit 10 and outdoor unit 20 are mutually connected as shown in FIGS. 1
and 9A. However, five misconnection cases shown in FIGS. 9B through 9F
are possible. Among others, in the case of the misconnection shown in
FIG. 9B, when the relay MR10 is turned on as indicated by the dashed
lines in FIG. 5B, a closed circuit including the external power source 30
is formed to damage the components (for example, the relay MR10). In the
misconnection cases of FIGS. 9C through 9F, no closed circuit including
the power source is formed, and the components are not damaged.

[0071]Accordingly, in the air conditioner of the first embodiment, the
indoor control section 12 determines whether or not the connection wiring
lines L1 through L3 that connect the indoor unit 10 with the outdoor unit
20 are miswired on the basis of a reception output of the indoor side
transmitting and receiving section 15 when the operation starts from the
standby state, and does not turn on the relay MRM10 when determining that
the wiring lines are miswired.

[0072]FIG. 6 shows a timing chart for explaining the processing when the
operation starts from the standby state of the air conditioner. Referring
to FIG. 6, FIG. 6(a) shows an operation start signal of the air
conditioner, FIG. 6(b) shows the reception output of the indoor side
transmitting and receiving section 15, FIG. 6(c) shows the operating
state of the relay MR10 in the case of miswiring, and FIG. 6(d) shows the
operating state of the relay MR10 when the wiring is correct.

[0073]As shown in FIG. 6, when the operation is first started by
manipulating a remote controller (not shown) of the indoor unit 10 in the
standby state (during operation stop), the indoor control section 12
receives an operation start signal (shown in FIG. 6(a)) and thereafter
confirms the reception output of the indoor side transmitting and
receiving section 15 after a lapse of a prescribed time (e.g., one
second). At this time, if the connection wiring lines are miswired as
shown in FIGS. 5A and 5B, the reception output of the indoor side
transmitting and receiving section 15 periodically repeats on- and
off-states as shown in FIG. 6(b). This is because an AC voltage is
applied to the connection wiring line L3 with a closed circuit formed as
shown in FIG. 5A so that the diode D151 of the indoor side transmitting
and receiving section 15 emits light every half wave (at intervals of 20
milliseconds at a frequency of 50 Hz) of the AC voltage.

[0074]The indoor control section 12 confirms the reception output of the
indoor side transmitting and receiving section 15 in cycles of several
milliseconds and does not turn on the relay MR10 upon determining that
the wiring lines are miswired when high level consecutively appears two
times as shown in FIG. 6(c). When the wiring lines are correctly wired,
the indoor control section 12 determines that the wiring lines are not
miswired since the reception output of the indoor side transmitting and
receiving section 15 is not turned on unless communication is carried
out, and turns on the relay MR10 for a prescribed time (e.g., several
tens of milliseconds) as shown in FIG. 6(d).

[0075]Upon determining that the wiring lines are miswired on the basis of
the reception output of the indoor side transmitting and receiving
section 15, the indoor control section 12 informs the user of the
miswiring by means of the display section 13.

[0076]According to the air conditioner of the first embodiment, damage of
the components can be prevented with a simple construction even if the
operation starts in the state in which the connection wiring lines (L1
through L3) that connect the indoor unit 10 with the outdoor unit 20 are
miswired.

[0077]Moreover, it becomes possible to easily determine that the
connection wiring lines (L1 through L3) are miswired before the relay
MR10 is turned on by the fact that the reception output of the indoor
side transmitting and receiving section 15 is turned on as a consequence
of applying the power voltage to the signal line L3 in the miswired state
shown in FIG. 5A.

[0078]Moreover, since the user is informed of the miswiring by the display
section 13 when the indoor control section 12 determines that the
connection wiring lines (L1 through L3) are miswired, the operator is
able to perceive the cause of the trouble at the time of installation and
to swiftly cope with the trouble.

SECOND EMBODIMENT

[0079]FIG. 7 is a block diagram of the air conditioner of the second
embodiment of the present invention, showing an indoor unit 10, an
outdoor unit 20 connected to the indoor unit 10 via connection wiring
lines (L1 through L3), and an external power source 30 connected to the
indoor unit 10.

[0080]The indoor unit 10 includes a power circuit 11 that has one terminal
connected to a power line L1 and has the other terminal connected to a
power line L2, an indoor side transmitting and receiving section 15 as
one example of the indoor side transmitting and receiving means that has
one terminal connected to one terminal of a signal line L3 and has the
other terminal connected to the power line L2, and a relay MR10 as one
example of the indoor side switch means that is normally in an open state
and connected between the power line L1 and the signal line L3. A power
voltage supplied from the external power source 30 is applied across both
terminals of the power circuit 11. The indoor unit 10 also includes an
indoor control section 12 as one example of the indoor control means that
is supplied with a power from a power circuit 11 and controls the relay
MR10 and so on, and a display section 13 as one example of the informing
means controlled by the indoor control section 12.

[0081]On the other hand, the outdoor unit 20 includes an EMI filter LC1
that have input terminals connected to the power lines L1 and L2, an
outdoor side transmitting and receiving section 25 as one example of the
outdoor side transmitting and receiving means connected to the other
terminal of the signal line L3, a transmission power circuit 24 that
supplies a power to the outdoor side transmitting and receiving section
25, a switching power circuit 22 connected to one terminal of the output
terminals of the EMI filter LC1 via a relay MRM10 as one example of the
operating power supply switch means, and a power circuit 23 as one
example of the load that has one terminal connected to one terminal of
the switching power circuit 22. One terminal of a switchover relay MR30
as one example of the startup power supply switch means is connected to
the signal line L3, and the other terminal of the switchover relay MR30
is connected to one terminal of the resistor R11. The other terminal of
the resistor R11 is connected to a connection point of the relay MRM10
and the switching power circuit 22. Moreover, the other terminal of the
switching power circuit 22 and the other terminal of the power circuit 23
are connected to the other terminal of the output terminals of the EMI
filter LC1. The outdoor unit 20 also includes an outdoor control section
21 as one example of the outdoor control means that is supplied with a
power from the switching power circuit 22 and controls the relay MRM10
and so on.

[0082]The indoor side transmitting and receiving section 15, the
transmission power circuit 24, the outdoor side transmitting and
receiving section 25 and the EMI filter LC1 have identical structures as
those of the air conditioner of the first embodiment, and no description
is provided for them.

[0083]As shown in FIG. 8, with regard to the relay MR10 of the indoor unit
10, the relay MR10 is closed by an indoor microcomputer 12 when the
operation is switched over from the standby state to the operating state,
so that the main power is supplied from the power line L1 to the signal
line L3. That is, the structure is similar to that of the first
embodiment in the point that the signal representing switchover from the
standby state to the operating state is a rise in the voltage of the
signal line L3.

[0084]In the air conditioner of the above construction, it is correct to
connect the wiring lines L1 through L3 at the time of installation in a
manner that the terminals AC, the terminals S and the terminals COM are
mutually connected as shown in FIGS. 7 and 9A. However, five
misconnection cases shown in FIGS. 9B through 9F are possible. Among
others, in the case of the misconnection shown in FIG. 9B, the components
are to be damaged.

[0085]Accordingly, in the air conditioner of the second embodiment, the
outdoor control section 21 brings the startup relay MR30 into the closed
state and thereafter turns on the relay MRM10 after a lapse of a
prescribed time (e.g., several tens of milliseconds) when the operation
starts from the standby state upon supplying a power for startup from the
indoor unit 10 side via the signal line L3 by turning on the relay MR10
of the indoor unit 10.

[0086]In detail, when the relay MR10 of the indoor unit 10 is turned on,
an AC voltage is applied to the signal line L3, so that a power is
supplied to the switching power circuit 22 via the switchover relay MR30
and the resistor R11 of the outdoor unit 20. Then, a DC voltage is
outputted from the switching power circuit 22 to the transmission power
circuit 24 and the outdoor control section 21. As a result, the outdoor
control section 21 that operates upon receiving the DC voltage from the
switching power circuit 22 brings the startup relay MR30 into the closed
state and thereafter turns on the relay MRM10 before the DC voltage
output of the switching power circuit 22 is spent and after a lapse of a
prescribed time (e.g., several tens of milliseconds). By so doing, the
power for operation from the indoor unit 10 side is supplied to the
switching power circuit 22 and the power circuit 23 via the power lines
L1 and L2.

[0087]According to the air conditioner of the second embodiment, damage of
the components can be prevented with a simple construction even if the
operation starts in the state in which the connection wiring lines (L1
through L3) that connect the indoor unit 10 with the outdoor unit 20 are
miswired.

[0088]Moreover, when no communication with the outdoor side transmitting
and receiving section 25 can be achieved by the indoor side transmitting
and receiving section 15 after the relay MR10 is turned on, the indoor
control section 12 determines that the connection wiring lines (L1
through L3) are miswired and informs the user of the miswiring by means
of the display section 13. Therefore, the operator is able to perceive
the cause of trouble at the time of installation and to swiftly cope with
the trouble.

[0089]Although the external power source 30 is connected to the indoor
unit 10 in the second embodiment, the external power source may be
connected to the outdoor unit.

[0090]Moreover, although the display section 13 is employed as the
informing means in the first and second embodiments, the informing means
is not limited to this and allowed to give information by means of a
voice sound or a buzzer sound.

[0091]The invention being thus described, it will be obvious that the same
may be varied in many ways. Such variations are not to be regarded as a
departure from the spirit and scope of the invention, and all such
modifications as would be obvious to one skilled in the art are intended
to be included within the scope of the following claims.